Thin skin under the eyes

Skin under the eyes is thinner than skin elsewhere (half a millimeter or less, as opposed to about two millimeters), and so is more transparent; it shows the blood vessels underneath more clearly than other skin does. Skin under the eyes may be even more transparent if it is pale due to anemia or pregnancy. The blood beneath it appears bluish rather than reddish because skin transmits blue light better than other colors. Thus skin around the eyes may appear bluish, brownish, or even greenish, depending on a persons basic skin color.